1. Field of the Invention
The present invention relates to a deposited film forming method and a deposited film forming apparatus and, more particularly, to a functional-deposited-film forming method of forming a stack element on a belt-like member by a roll to roll system and an apparatus for carrying out the method.
2. Related Background Art
As a method of continuously forming a functional deposited film of a semiconductor or the like for use in a photovoltaic element or the like on a substrate, there is known a method wherein there are provided independent film-forming chambers for formation of various semiconductor layers, these film-forming chambers are coupled by a load lock system through a gate valve, and the substrate is successively moved through the film-forming chambers to form various semiconductor layers on the substrate. As a method for remarkably enhancing mass productivity, U.S. Pat. No. 4,400,409 discloses a continuous plasma CVD process employing the so-called roll to roll system. This process is described as using a long magnetic belt-like member as a substrate, in which the substrate is continuously conveyed in the longitudinal direction thereof while desired conductive semiconductor layers are deposited in a plurality of glow discharge regions, whereby elements with semiconductor junctions can be continuously formed.
U.S. Pat. No. 4,462,333 discloses a continuous plasma CVD process employing the roll to roll system, in which a deposited film is formed by the use of a double chamber system wherein a pair of top plates with an aperture cover the edges of a substrate. Japanese Patent Application Laid-Open No. 9-162133 describes an invention titled xe2x80x9ccontinuous forming method and apparatus of functional deposited filmsxe2x80x9d in which a semiconductor film is deposited by a plasma CVD process with means for preventing leakage and diffusion of a discharge and an activated gas. It is described that in this apparatus a belt-like member constitutes a member for partitioning an activation region, and a member provided widthwise outside the belt-like member, for partitioning off the activation region is kept in contact with a back surface opposite to a deposited film forming surface of the belt-like member to prevent leakage and diffusion of a discharge and an activated gas. Further, Japanese Patent Application Laid-Open No. 2000-160345 discloses an invention titled xe2x80x9cfunctional-deposited-film forming method and forming apparatus thereforxe2x80x9d in which a top plate is kept in contact with a belt-like member to keep the belt-like member well at the earth potential relative to high-frequency waves, thereby stabilizing a discharge.
In these methods of continuously forming a functional deposited film of a semiconductor or the like for use in a photovoltaic element or the like on a substrate, efforts have been made to enhance the photoelectric conversion efficiency, characteristic stability, or characteristic uniformity, or to reduce the production cost, or the like. In these methods, however, an attempt for increasing the conveyance speed of a belt-like member resulted in occurrence of unevenness of the surface of the belt-like member due to fine undulation at the edges in the width (cross) direction of the belt-like member, or a gap of the discharge space generated by the unevenness and the change thereof to which the shapes of surrounding components failed to correspond. This sometimes caused a leakage of the discharge to degrade the discharge stability and characteristic uniformity.
When a semiconductor thin film was formed on a belt-like member with application of a bias in addition to application of a high-frequency power, sparks were generated because of a change in the contact state of the belt-like member with surrounding components due to the fine undulation or unevenness of the edges in the width direction of the belt-like member, or the vibration of the belt-like member itself.
Further, the undulation and unevenness of the width-direction edges of the belt-like member will always vary in the longitudinal direction thereof as well and the mechanical property and shape of the belt-like member supplied from a substrate roll will vary from roll to roll when replacing the belt-like member. It was thus difficult to preliminarily set the conventional surrounding components so as to adapt to the variations.
The present invention has been accomplished to solve the problem in the prior art as described above, and an object of the present invention is, therefore, to provide a deposited film forming method and a deposited film forming apparatus capable of decreasing the discharge leakage and sparks and maintaining a stable discharge even during high-speed conveyance, with increase in the film-forming speed, with replacement of the roll, or the like and, particularly, to provide a functional-deposited-film forming method and a functional-deposited-film forming apparatus enabling formation of amorphous silicon films that are excellent in electrical and optical characteristics and that can increase the yield of elements in mass production.
In order to achieve the above object, the present invention provides a deposited film forming method and a deposited film forming apparatus configured as in (1) to (10) below.
(1) A deposited film forming method of, while continuously conveying a belt-like member in a longitudinal direction thereof, passing the belt-like member through a film-forming chamber, one side of which is formed of the belt-like member and which is located in a vacuum-sealable reaction vessel, introducing a reactive gas into the film-forming chamber, evacuating the interior of the film-forming chamber by evacuation means to maintain the interior of the film-forming chamber at a given pressure, introducing a high-frequency power into the film-forming chamber to induce a plasma, and forming a deposited film on the belt-like member passing through the film-forming chamber,
wherein on a side opposite to a deposited film forming side of the belt-like member that forms the said one side of the film-forming chamber, there is provided discharge confining means always maintaining contact with the said opposite side of the belt-like member while following a change in shape of the belt-like member, whereby the deposited film is formed in a state of reduced discharge leakage and sparks in the film-forming chamber.
(2) The method according to above (1), wherein the discharge confining means is comprised of a member always maintaining contact with the said opposite side of the belt-like member by at least one of elasticity, pressure, gravity, and magnetism.
(3) The method according to above (2), wherein the member is of a store curtain shape, saw-tooth shape, spring shape, brush shape, roller shape, or hinge shape.
(4) The method according to any one of above (1) to (3), wherein the discharge confining means is electrically conductive.
(5) The method according to above (4), wherein the high-frequency power introduced into the film-forming chamber has a frequency of not less than 10 MHz nor more than 10 GHz.
(6) A deposited film forming apparatus comprising means for continuously conveying a substrate consisting of a belt-like member for formation of a deposited film, in a longitudinal direction thereof: a vacuum-sealable reaction vessel having therein a film-forming chamber, one side of which is constituted of the belt-like member; means for introducing a reactive gas into the film-forming chamber; means for introducing a high-frequency power from a high-frequency power supply into the film-forming chamber; and means for evacuating the interior of the film-forming chamber,
wherein on a side opposite to a deposited film forming side of the belt-like member that forms said one side of the film-forming chamber, there is provided discharge confining means always maintaining contact with said opposite side of the belt-like member while following a change in shape of the belt-like member.
(7) The apparatus according to above (6), wherein the discharge confining means is comprised of a member always maintaining contact with the opposite side of the belt-like member by at least one of elasticity, pressure, gravity, and magnetism.
(8) The apparatus according to above (7), wherein the member is of a store curtain shape, saw-tooth shape, spring shape, brush shape, roller shape, or hinge shape.
(9) The apparatus according to any one of above (6) to (8), wherein the discharge confining means is electrically conductive.
(10) The apparatus according to above (9), wherein the high-frequency power introduced into the film-forming chamber has a frequency of not less than 10 MHz nor more than 10 GHz.